The present disclosure relates to exhaust gas-driven turbochargers.
In a typical turbocharger there is a compressor housing, a center housing, and a turbine housing. The compressor housing defines a volute that collects pressurized air from the compressor wheel for onward delivery to the air intake of an internal combustion engine. The center housing's main role is to house bearings for the shaft that connects the compressor wheel to the turbine wheel. The turbine housing defines a volute that receives exhaust gas from the engine and directs it into the turbine wheel, which is thereby driven to rotate and drive the compressor wheel.
Conventionally, all of the turbocharger housing members are separate components. The compressor housing typically defines not only the compressor volute but also a diffuser that receives pressurized air from the compressor wheel and diffuses it before delivering it into the volute. The diffuser is important in terms of compressor efficiency. In particular, it is important that the diffuser have the dimensions specified by the compressor designer, and accordingly it is generally necessary to machine the diffuser in order to achieve the accuracy that is needed. Such machining is difficult, however, because of the diffuser's location in the casting for the compressor housing.
The machining difficulty is exacerbated when the compressor volute is integrated into an engine cylinder head, as is the case with more-recently proposed turbocharger designs (as described, for example, in the above-noted '891 and '943 applications related to the present disclosure) in which such integration is employed in order to simplify manufacture of the turbocharger and its incorporation into the engine system.